gdb/exceptions.c

   1 /* Exception (throw catch) mechanism, for GDB, the GNU debugger.
   2
   3    Copyright 1986, 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995,
   4    1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005 Free
   5    Software Foundation, Inc.
   6
   7    This file is part of GDB.
   8
   9    This program is free software; you can redistribute it and/or modify
  10    it under the terms of the GNU General Public License as published by
  11    the Free Software Foundation; either version 2 of the License, or
  12    (at your option) any later version.
  13
  14    This program is distributed in the hope that it will be useful,
  15    but WITHOUT ANY WARRANTY; without even the implied warranty of
  16    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17    GNU General Public License for more details.
  18
  19    You should have received a copy of the GNU General Public License
  20    along with this program; if not, write to the Free Software
  21    Foundation, Inc., 59 Temple Place - Suite 330,
  22    Boston, MA 02111-1307, USA.  */
  23
  24 #include "defs.h"
  25 #include "exceptions.h"
  26 #include <setjmp.h>
  27 #include "breakpoint.h"
  28 #include "target.h"
  29 #include "inferior.h"
  30 #include "annotate.h"
  31 #include "ui-out.h"
  32 #include "gdb_assert.h"
  33 #include "gdb_string.h"
  34 #include "serial.h"
  35
  36 const struct exception exception_none = { 0, NO_ERROR, NULL };
  37
  38 /* One should use catch_errors rather than manipulating these
  39    directly.  */
  40 #if defined(HAVE_SIGSETJMP)
  41 #define SIGJMP_BUF              sigjmp_buf
  42 #define SIGSETJMP(buf)          sigsetjmp((buf), 1)
  43 #define SIGLONGJMP(buf,val)     siglongjmp((buf), (val))
  44 #else
  45 #define SIGJMP_BUF              jmp_buf
  46 #define SIGSETJMP(buf)          setjmp(buf)
  47 #define SIGLONGJMP(buf,val)     longjmp((buf), (val))
  48 #endif
  49
  50 /* Possible catcher states.  */
  51 enum catcher_state {
  52   /* Initial state, a new catcher has just been created.  */
  53   CATCHER_CREATED,
  54   /* The catch code is running.  */
  55   CATCHER_RUNNING,
  56   CATCHER_RUNNING_1,
  57   /* The catch code threw an exception.  */
  58   CATCHER_ABORTING
  59 };
  60
  61 /* Possible catcher actions.  */
  62 enum catcher_action {
  63   CATCH_ITER,
  64   CATCH_ITER_1,
  65   CATCH_THROWING
  66 };
  67
  68 struct catcher
  69 {
  70   enum catcher_state state;
  71   /* Jump buffer pointing back at the exception handler.  */
  72   SIGJMP_BUF buf;
  73   /* Status buffer belonging to the exception handler.  */
  74   volatile struct exception *exception;
  75   /* Saved/current state.  */
  76   int mask;
  77   struct ui_out *saved_uiout;
  78   struct cleanup *saved_cleanup_chain;
  79   /* Back link.  */
  80   struct catcher *prev;
  81 };
  82
  83 /* Where to go for throw_exception().  */
  84 static struct catcher *current_catcher;
  85
  86 static SIGJMP_BUF *
  87 catcher_init (struct ui_out *func_uiout,
  88               volatile struct exception *exception,
  89               return_mask mask)
  90 {
  91   struct catcher *new_catcher = XZALLOC (struct catcher);
  92
  93   /* Start with no exception, save it's address.  */
  94   exception->reason = 0;
  95   exception->error = NO_ERROR;
  96   exception->message = NULL;
  97   new_catcher->exception = exception;
  98
  99   new_catcher->mask = mask;
 100
 101   /* Override the global ``struct ui_out'' builder.  */
 102   new_catcher->saved_uiout = uiout;
 103   uiout = func_uiout;
 104
 105   /* Prevent error/quit during FUNC from calling cleanups established
 106      prior to here. */
 107   new_catcher->saved_cleanup_chain = save_cleanups ();
 108
 109   /* Push this new catcher on the top.  */
 110   new_catcher->prev = current_catcher;
 111   current_catcher = new_catcher;
 112   new_catcher->state = CATCHER_CREATED;
 113
 114   return &new_catcher->buf;
 115 }
 116
 117 static void
 118 catcher_pop (void)
 119 {
 120   struct catcher *old_catcher = current_catcher;
 121   current_catcher = old_catcher->prev;
 122
 123   /* Restore the cleanup chain, the error/quit messages, and the uiout
 124      builder, to their original states. */
 125
 126   restore_cleanups (old_catcher->saved_cleanup_chain);
 127
 128   uiout = old_catcher->saved_uiout;
 129
 130   xfree (old_catcher);
 131 }
 132
 133 /* Catcher state machine.  Returns non-zero if the m/c should be run
 134    again, zero if it should abort.  */
 135
 136 int
 137 catcher_state_machine (enum catcher_action action)
 138 {
 139   switch (current_catcher->state)
 140     {
 141     case CATCHER_CREATED:
 142       switch (action)
 143         {
 144         case CATCH_ITER:
 145           /* Allow the code to run the catcher.  */
 146           current_catcher->state = CATCHER_RUNNING;
 147           return 1;
 148         default:
 149           internal_error (__FILE__, __LINE__, "bad state");
 150         }
 151     case CATCHER_RUNNING:
 152       switch (action)
 153         {
 154         case CATCH_ITER:
 155           /* No error/quit has occured.  Just clean up.  */
 156           catcher_pop ();
 157           return 0;
 158         case CATCH_ITER_1:
 159           current_catcher->state = CATCHER_RUNNING_1;
 160           return 1;
 161         case CATCH_THROWING:
 162           current_catcher->state = CATCHER_ABORTING;
 163           /* See also throw_exception.  */
 164           return 1;
 165         default:
 166           internal_error (__FILE__, __LINE__, "bad switch");
 167         }
 168     case CATCHER_RUNNING_1:
 169       switch (action)
 170         {
 171         case CATCH_ITER:
 172           /* The did a "break" from the inner while loop.  */
 173           catcher_pop ();
 174           return 0;
 175         case CATCH_ITER_1:
 176           current_catcher->state = CATCHER_RUNNING;
 177           return 0;
 178         case CATCH_THROWING:
 179           current_catcher->state = CATCHER_ABORTING;
 180           /* See also throw_exception.  */
 181           return 1;
 182         default:
 183           internal_error (__FILE__, __LINE__, "bad switch");
 184         }
 185     case CATCHER_ABORTING:
 186       switch (action)
 187         {
 188         case CATCH_ITER:
 189           {
 190             struct exception exception = *current_catcher->exception;
 191             if (current_catcher->mask & RETURN_MASK (exception.reason))
 192               {
 193                 /* Exit normally if this catcher can handle this
 194                    exception.  The caller analyses the func return
 195                    values.  */
 196                 catcher_pop ();
 197                 return 0;
 198               }
 199             /* The caller didn't request that the event be caught,
 200                relay the event to the next containing
 201                catch_errors(). */
 202             catcher_pop ();
 203             throw_exception (exception);
 204           }
 205         default:
 206           internal_error (__FILE__, __LINE__, "bad state");
 207         }
 208     default:
 209       internal_error (__FILE__, __LINE__, "bad switch");
 210     }
 211 }
 212
 213 /* Return EXCEPTION to the nearest containing catch_errors().  */
 214
 215 NORETURN void
 216 throw_exception (struct exception exception)
 217 {
 218   quit_flag = 0;
 219   immediate_quit = 0;
 220
 221   /* Perhaps it would be cleaner to do this via the cleanup chain (not sure
 222      I can think of a reason why that is vital, though).  */
 223   bpstat_clear_actions (stop_bpstat);   /* Clear queued breakpoint commands */
 224
 225   disable_current_display ();
 226   do_cleanups (ALL_CLEANUPS);
 227   if (target_can_async_p () && !target_executing)
 228     do_exec_cleanups (ALL_CLEANUPS);
 229   if (sync_execution)
 230     do_exec_error_cleanups (ALL_CLEANUPS);
 231
 232   /* Jump to the containing catch_errors() call, communicating REASON
 233      to that call via setjmp's return value.  Note that REASON can't
 234      be zero, by definition in defs.h. */
 235   catcher_state_machine (CATCH_THROWING);
 236   *current_catcher->exception = exception;
 237   SIGLONGJMP (current_catcher->buf, exception.reason);
 238 }
 239
 240 static char *last_message;
 241
 242 NORETURN void
 243 deprecated_throw_reason (enum return_reason reason)
 244 {
 245   struct exception exception;
 246   memset (&exception, 0, sizeof exception);
 247
 248   exception.reason = reason;
 249   switch (reason)
 250     {
 251     case RETURN_QUIT:
 252       break;
 253     case RETURN_ERROR:
 254       exception.error = GENERIC_ERROR;
 255       break;
 256     default:
 257       internal_error (__FILE__, __LINE__, "bad switch");
 258     }
 259
 260   throw_exception (exception);
 261 }
 262
 263 static void
 264 print_flush (void)
 265 {
 266   struct serial *gdb_stdout_serial;
 267
 268   if (deprecated_error_begin_hook)
 269     deprecated_error_begin_hook ();
 270   target_terminal_ours ();
 271
 272   /* We want all output to appear now, before we print the error.  We
 273      have 3 levels of buffering we have to flush (it's possible that
 274      some of these should be changed to flush the lower-level ones
 275      too):  */
 276
 277   /* 1.  The _filtered buffer.  */
 278   wrap_here ("");
 279
 280   /* 2.  The stdio buffer.  */
 281   gdb_flush (gdb_stdout);
 282   gdb_flush (gdb_stderr);
 283
 284   /* 3.  The system-level buffer.  */
 285   gdb_stdout_serial = serial_fdopen (1);
 286   serial_drain_output (gdb_stdout_serial);
 287   serial_un_fdopen (gdb_stdout_serial);
 288
 289   annotate_error_begin ();
 290 }
 291
 292 static void
 293 print_exception (struct ui_file *file, struct exception e)
 294 {
 295   /* KLUGE: cagney/2005-01-13: Write the string out one line at a time
 296      as that way the MI's behavior is preserved.  */
 297   const char *start;
 298   const char *end;
 299   for (start = e.message; start != NULL; start = end)
 300     {
 301       end = strchr (start, '\n');
 302       if (end == NULL)
 303         fputs_filtered (start, file);
 304       else
 305         {
 306           end++;
 307           ui_file_write (file, start, end - start);
 308         }
 309     }
 310   fprintf_filtered (file, "\n");
 311
 312   /* Now append the annotation.  */
 313   switch (e.reason)
 314     {
 315     case RETURN_QUIT:
 316       annotate_quit ();
 317       break;
 318     case RETURN_ERROR:
 319       /* Assume that these are all errors.  */
 320       annotate_error ();
 321       break;
 322     default:
 323       internal_error (__FILE__, __LINE__, _("Bad switch."));
 324     }
 325 }
 326
 327 void
 328 exception_print (struct ui_file *file, struct exception e)
 329 {
 330   if (e.reason < 0 && e.message != NULL)
 331     {
 332       print_flush ();
 333       print_exception (file, e);
 334     }
 335 }
 336
 337 void
 338 exception_fprintf (struct ui_file *file, struct exception e,
 339                    const char *prefix, ...)
 340 {
 341   if (e.reason < 0 && e.message != NULL)
 342     {
 343       va_list args;
 344
 345       print_flush ();
 346
 347       /* Print the prefix.  */
 348       va_start (args, prefix);
 349       vfprintf_filtered (file, prefix, args);
 350       va_end (args);
 351
 352       print_exception (file, e);
 353     }
 354 }
 355
 356 void
 357 print_any_exception (struct ui_file *file, const char *prefix,
 358                      struct exception e)
 359 {
 360   if (e.reason < 0 && e.message != NULL)
 361     {
 362       target_terminal_ours ();
 363       wrap_here ("");           /* Force out any buffered output */
 364       gdb_flush (gdb_stdout);
 365       annotate_error_begin ();
 366
 367       /* Print the prefix.  */
 368       if (prefix != NULL && prefix[0] != '\0')
 369         fputs_filtered (prefix, file);
 370       print_exception (file, e);
 371     }
 372 }
 373
 374 NORETURN static void
 375 throw_it (enum return_reason reason, enum errors error, const char *fmt,
 376           va_list ap) ATTR_NORETURN;
 377 NORETURN static void
 378 throw_it (enum return_reason reason, enum errors error, const char *fmt,
 379           va_list ap)
 380 {
 381   struct exception e;
 382   char *new_message;
 383
 384   /* Save the message.  Create the new message before deleting the
 385      old, the new message may include the old message text.  */
 386   new_message = xstrvprintf (fmt, ap);
 387   xfree (last_message);
 388   last_message = new_message;
 389
 390   /* Create the exception.  */
 391   e.reason = reason;
 392   e.error = error;
 393   e.message = last_message;
 394
 395   /* Throw the exception.  */
 396   throw_exception (e);
 397 }
 398
 399 NORETURN void
 400 throw_verror (enum errors error, const char *fmt, va_list ap)
 401 {
 402   throw_it (RETURN_ERROR, error, fmt, ap);
 403 }
 404
 405 NORETURN void
 406 throw_vfatal (const char *fmt, va_list ap)
 407 {
 408   throw_it (RETURN_QUIT, NO_ERROR, fmt, ap);
 409 }
 410
 411 NORETURN void
 412 throw_error (enum errors error, const char *fmt, ...)
 413 {
 414   va_list args;
 415   va_start (args, fmt);
 416   throw_it (RETURN_ERROR, error, fmt, args);
 417   va_end (args);
 418 }
 419
 420 /* Call FUNC() with args FUNC_UIOUT and FUNC_ARGS, catching any
 421    errors.  Set FUNC_CAUGHT to an ``enum return_reason'' if the
 422    function is aborted (using throw_exception() or zero if the
 423    function returns normally.  Set FUNC_VAL to the value returned by
 424    the function or 0 if the function was aborted.
 425
 426    Must not be called with immediate_quit in effect (bad things might
 427    happen, say we got a signal in the middle of a memcpy to quit_return).
 428    This is an OK restriction; with very few exceptions immediate_quit can
 429    be replaced by judicious use of QUIT.
 430
 431    MASK specifies what to catch; it is normally set to
 432    RETURN_MASK_ALL, if for no other reason than that the code which
 433    calls catch_errors might not be set up to deal with a quit which
 434    isn't caught.  But if the code can deal with it, it generally
 435    should be RETURN_MASK_ERROR, unless for some reason it is more
 436    useful to abort only the portion of the operation inside the
 437    catch_errors.  Note that quit should return to the command line
 438    fairly quickly, even if some further processing is being done.  */
 439
 440 /* MAYBE: cagney/1999-11-05: catch_errors() in conjunction with
 441    error() et.al. could maintain a set of flags that indicate the the
 442    current state of each of the longjmp buffers.  This would give the
 443    longjmp code the chance to detect a longjmp botch (before it gets
 444    to longjmperror()).  Prior to 1999-11-05 this wasn't possible as
 445    code also randomly used a SET_TOP_LEVEL macro that directly
 446    initialize the longjmp buffers. */
 447
 448 /* MAYBE: cagney/1999-11-05: Should the catch_errors and cleanups code
 449    be consolidated into a single file instead of being distributed
 450    between utils.c and top.c? */
 451
 452 int
 453 catch_exceptions (struct ui_out *uiout,
 454                   catch_exceptions_ftype *func,
 455                   void *func_args,
 456                   return_mask mask)
 457 {
 458   return catch_exceptions_with_msg (uiout, func, func_args, NULL, mask);
 459 }
 460
 461 struct exception
 462 catch_exception (struct ui_out *uiout,
 463                  catch_exception_ftype *func,
 464                  void *func_args,
 465                  return_mask mask)
 466 {
 467   volatile struct exception exception;
 468   SIGJMP_BUF *catch;
 469   catch = catcher_init (uiout, &exception, mask);
 470   for (SIGSETJMP ((*catch));
 471        catcher_state_machine (CATCH_ITER);)
 472     (*func) (uiout, func_args);
 473   return exception;
 474 }
 475
 476 int
 477 catch_exceptions_with_msg (struct ui_out *uiout,
 478                            catch_exceptions_ftype *func,
 479                            void *func_args,
 480                            char **gdberrmsg,
 481                            return_mask mask)
 482 {
 483   volatile struct exception exception;
 484   volatile int val = 0;
 485   SIGJMP_BUF *catch = catcher_init (uiout, &exception, mask);
 486   for (SIGSETJMP ((*catch)); catcher_state_machine (CATCH_ITER);)
 487     val = (*func) (uiout, func_args);
 488   print_any_exception (gdb_stderr, NULL, exception);
 489   gdb_assert (val >= 0);
 490   gdb_assert (exception.reason <= 0);
 491   if (exception.reason < 0)
 492     {
 493       /* If caller wants a copy of the low-level error message, make
 494          one.  This is used in the case of a silent error whereby the
 495          caller may optionally want to issue the message.  */
 496       if (gdberrmsg != NULL)
 497         {
 498           if (exception.message != NULL)
 499             *gdberrmsg = xstrdup (exception.message);
 500           else
 501             *gdberrmsg = NULL;
 502         }
 503       return exception.reason;
 504     }
 505   return val;
 506 }
 507
 508 int
 509 catch_errors (catch_errors_ftype *func, void *func_args, char *errstring,
 510               return_mask mask)
 511 {
 512   volatile int val = 0;
 513   volatile struct exception exception;
 514   SIGJMP_BUF *catch = catcher_init (uiout, &exception, mask);
 515   /* This illustrates how it is possible to nest the mechanism and
 516      hence catch "break".  Of course this doesn't address the need to
 517      also catch "return".  */
 518   for (SIGSETJMP ((*catch)); catcher_state_machine (CATCH_ITER);)
 519     val = func (func_args);
 520   print_any_exception (gdb_stderr, errstring, exception);
 521   if (exception.reason != 0)
 522     return 0;
 523   return val;
 524 }
 525
 526 int
 527 catch_command_errors (catch_command_errors_ftype * command,
 528                       char *arg, int from_tty, return_mask mask)
 529 {
 530   volatile struct exception e;
 531   SIGJMP_BUF *catch = catcher_init (uiout, &e, mask);
 532   for (SIGSETJMP ((*catch)); catcher_state_machine (CATCH_ITER);)
 533     command (arg, from_tty);
 534   print_any_exception (gdb_stderr, NULL, e);
 535   if (e.reason < 0)
 536     return 0;
 537   return 1;
 538 }